1. Field of the Invention
The present invention relates to a diaphragm spring for a friction clutch, comprising a ring-like body area and a plurality of radially inward-extending spring tongues, arranged in a row in the circumferential direction, where openings which terminate in a radially outer base area are formed between adjacent spring tongues.
2. Description of the Related Art
These types of diaphragm springs are used in friction clutches to provide the pretensioning forces required in the engaged state of the clutch by supporting themselves against a housing on one side and against a pressure plate on the other. A clutch-release mechanism can act in the area of the radially inward-extending spring tongues, so that these tongues can serve essentially as actuating levers.
It is known that the openings which separate the individual spring tongues in the circumferential direction can be designed in their radially outer area, that is, in the area near the base, with, for example, a circular terminal contour or with a straight base, that is, a base which is approximately tangential and which is adjoined by circular sections.
A problem with these types of diaphragm springs is that, as a result of the geometry of the usually slightly umbrella-shaped, that is, conically designed, diaphragm spring, stresses which limit the maximum elastic force and thus also the maximum clutch-engaging force occur in the radially inner part of the ring-like body area.